The present invention relates to an apparatus for sieving a particulate material into selected size fractions.
The present invention relates particularly, although by no means exclusively, to an apparatus for sieving diamonds into selected size fractions.
The conventional apparatus for sieving diamonds into selected size fractions comprises an assembly of vibrating screens that are arranged in a stack with the uppermost screen having the largest screen size and successive screens having progressively finer screen sizes.
The conventional apparatus is operated on a batch basis and, as a consequence, the apparatus generally is not compatible with upstream and downstream diamond processing steps which are usually operated on a continuous basis. Another disadvantage of the conventional apparatus is that the screens block readily due to diamonds becoming lodged in holes in the screens ("pegged"). As a consequence, pegged diamonds must be removed from the screen holes periodically to maintain optimum performance of the screens. In addition to this being a time-consuming and labour intensive exercise, there is generally a degradation of product caused by diamonds being broken during the de-pegging operation. Other disadvantages of the conventional apparatus are high noise and dust levels.